The present invention relates to a machine for handling and separation welding of a web of material. More particularly, the present invention relates to a machine for the manufacturing of plastic bags from a web of thermoplastic synthetic material which has been folded once around one of its longitudinal axes, in which the welding tool separates the individual bags from each other and thereby simultaneously produces the side seams of the bags.
From West German Pat. No. 1,479,807 a machine is known which uses a transfer gearing consisting of a universal joint shaft in which the pivot pins fastened to the two ends of the shaft are perpendicular to each other. In this way uniform rotation of a drive shaft is transformed into non-uniform rotation of a driven shaft of the transfer gearing. By changing the inclination of the universal joint shaft with respect to the drive shaft, the non-uniformity of rotation of the driven shaft of the transfer gearing can be adjusted. In this apparatus, the web of material is driven at a constant speed. When the inclination of the universal joint shaft is zero, the non-uniformity of the rotation of the driven shaft of the transfer gearing is also zero. If the universal joint shaft is operated with zero inclination, the longest sections of web are fed past the welding apparatus between welds thus producing the widest bags. Narrower bags are produced by increasing the speed of rotation of the welding tool and thus of the transfer gearing by changing the inclination of the universal joint shaft so that its minimum speed corresponds to the speed of the web of material. In order to produce shorter sections it is therefore necessary to simultaneously adjust the non-uniformity of the rotary motion produced at the driven shaft of the transfer gearing and increase the speed of rotation thereof. The non-uniformity of the rotation of the driven shaft of the transfer gearing subjects the drive to loads due to the accelerations and decelerations cyclically produced thereby. This additional load increases with an increase in the non-uniformity. Since, however, the accelerations also increase with the speed of rotation of the transfer gearing, the drive of the machine is subjected to a double load by the combination of these two factors, namely the increase in the uniformity and the increase in the speed of rotation.
The use of such a universal joint shaft has the disadvantage that the driven shaft carries out the cyclically repeated non-uniform movement twice during each rotation of the drive shaft. In order therefore to drive the welding tool via a universal joint shaft, the drive must rotate at half the speed of rotation of the welding tool, which is disadvantageous. Furthermore, the possibility of changing the spacing between the welds is relatively limited.